For example, a cut valve and a fuel tank overfilling restriction valve are mounted in a fuel tank of a motor vehicle. The cut valve prevents fuel in the fuel tank from leaking to the outside thereof when the motor vehicle turns or is inclined. The fuel tank overfilling restriction valve stops the filling of fuel into the fuel tank at an upper limit value for a specified filling capacity of the fuel tank when fuelling the fuel tank.
For example, Patent Document 1 describes a check valve integrated cut valve which has: a main body case formed of a circumferential wall and an upper wall for accommodation of a float valve; a circular vent hole formed in a central portion of the upper wall; a cylindrical portion elected from the upper wall of the main body case at the outer circumference of the vent hole; a cap member securely fitted over an upper opening portion in the cylindrical portion; a positive pressure valve disposed above the vent hole so as to contact therewith and go apart therefrom; and a negative pressure valve disposed so as to contact with and go apart from an opening portion in the positive pressure valve. A lower circumferential edge of the vent hole formed in the upper wall forms a valve seat, so that an upwardly-projecting centrally-located valve head of the valve float is allowed to contact with and go apart from the valve seat. Further, axially-extending guide ribs are formed at even circumferential intervals on an inner circumference of the cylindrical portion that is erected from the outer circumference of the vent hole so as to guide the upward/downward movement of the positive pressure valve.
When the fuel level in the fuel tank raises as a result of the vehicle oscillating or turning to submerge the float valve, the float valve is caused to float, and the valve head thereof abuts an inner circumference of the valve seat to close the vent hole, thereby preventing the fuel from leaking to the outside of the fuel tank. In addition, when the pressure inside the fuel tank is increased, the positive pressure valve raises to move apart from the vent hole, and fuel vapors within the fuel tank are discharged therefrom. On the other hand, when the pressure inside the fuel tank is reduced, the negative pressure valve is pushed down by the atmospheric pressure to move apart from the opening portion of the positive pressure valve, and outside air is introduced into the fuel tank through the opening portion and the vent hole, thereby adjusting the pressure inside the fuel tank.